Method of installing piles for resisting upward soil movements



April 30, 1963 L. HART ETAL METHOD OF INSTALLING PILES FOR RESISTINGUPWARD SOIL MOVEMENTS Filed Aug. 26, 1957 3 Sheets-Sheet 1 .R. 5. mm H WW MWHW M NWM m N R R LAB H April 30, 1963 L. HART ETAL 3,087,308

METHOD OF INSTALLING PILES FOR RESISTING UPWARD SOIL MOVEMENTS 5Sheets-Sheet 2 Filed Aug. 26, 1957 '27 INVENTORS.

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| HART ETAL 3,087,308

TALLING FILES FOR RESISTING UPW RD son MOVEM ENTS April 30, 1963 METHODOF INSA 3 Sheets-Sheet 5 Filed Aug. 26, 1957 l ENTORS. Luvro %A FP7THARRYWD.HUNTEI.

ATTORNEYS.

United States Patent 3,087,308 METHOD OF INSTALLING PILES FOR RESISTINGUPWARD SOIL MOVEMENTS Linton Hart and Harry W. D. Hunter, Birmingham,

Mich., assignors to Raymond International Inc, New

York, N.Y., a corporation of New Jersey Filed Aug. 26, 1957, Ser. No.680,156 3 Claims. (Cl. 61-5352) This invention relates to pile andfoundation constructions and methods for installing same in such formthat same will provide effective means not only for the usual purpose ofsupporting buildings or other structures, but also the additionalpurpose of preventing undesired displacement and upward movements of thesoil through which the piles are driven.

In the construction of foundations for large buildings and otherpurposes, under certain design conditions, deep pits must be excavatedto provide space for sub-basement foundations. Where the soil in whichsuch foundations are to be constructed is of an unstable nature suchthat it will move objectionably under differences in pressure and wherestructures exist near or adjacent to the construction site so as to beendangered by the consequent relief of soil pressures in the vicinity,it may be necessary to make provision against upheavals of the soil inthe areas where deep foundations are being constructed.

Heretofore when such problems have arisen, it has oftentimes been thepractice to install a caisson such that it will be provided at its lowerportion with a bell formation at the level of the hardpan layer in theearth, such caisson being reinforced down into the bell formation andarranged in such a way that the uplift forces in the surrounding earthare transferred to and resisted by the caisson shaft when the upliftpressure of the earth is applied to the base slab of the foundation atthe top of the caisson, the uplift pressure thence being transferreddown to the bell formation, and upward movement of the latter being inturn resisted by the load of clay or other earth thereabove. However,the installation of such caissons is often not practicable because ofinconveniences and expense factor or because of the soil conditions atthe hardpan level, which may be of of a granular or permeable character,not suited for constructing the bell formation particularly in thepresence of water.

In accordance with the present invention, the aboveindicated problem isovercome by controlling the upheaval of the surrounding earth by the useof piles or the like of a type which will herein be referred to asuplift piles, that is, piles or the like which are so constructed andinstalled as effectively to resist the upward movement of thesurrounding soil by anchoring the lower ends of the piles or pile groupsin bedrock, while the upper ends are anchored in the concrete footingfor the structure being built thereon. In accordance with preferredforms of the invention, with the lower ends of the piles anchored inbedrock, post-tensioned reinforcing means is provided, such means beinganchored with respect to the bedrock and extending up through the pileto the region of the tops of the piles and there anchored with respectto the concrete footing. Thus any upward pressures which tend to beapplied by the soil surrounding the piles and against the underside ofthe concrete footing, will be effectively resisted, because the concretefooting will be effectively anchored by the post-tensioned pilestructures to the bedrock below the soil. Also to some degree, since thepile is securely anchored against rising, it will resist rising of thesurrounding soil by reason of frictional resistance of the soil againstthe sides of the pile and by reason of the pressure of the soil againstthe boot on the lower end of the pile shell. Danger to any surroundingbuildings or structures, due to the tend- "ice ency of the soil to shiftinto the area or pit for the new construction, will thus be prevented,because such soil 'will be held against upheaval and thus retainedagainst release of its pressure which holds in place the soil adjacentthe surrounding building foundations.

The invention makes possible pile constructions which can carry out theabove-indicated purposes while making possible increased speeds offoundation construction with reduced costs and without interfering withthe usual purpose of normal piles of providing reliable load-bearingsupports firmly resistant against the heavy downward pressures ofbuildings or other structures when completed and resting thereon.

Various further and more specific objects, features and advantages ofthe invention will appear from the description given below, taken inconnection with the accompanying drawings, illustrating by way ofexample preferred forms of the invention.

In the drawings:

FIG. 1 is a vertical sectional view of a typical pile and foundationinstallation embodying the invention;

FIG. 2 is a View showing the lower end portion of one of the pilespartially in section, and a preferred means for anchoring same inbedrocks;

FIG. 3 is an enlarged view of one typical and possible form of anchoragemeans for the lower end of the pile, this view being shown in sectiontaken substantially along line 3--3 of FIG. 5;

FIG. 4 is an elevational view of the lower end portion of said anchoragemeans;

FIG. 4a illustrates in perspective certain of the separate portions ofthe assembly of FIG. 4. 4

FIG. 5 is a horizontal sectional view taken substantially along line 55of FIG. 4;

FIG. 6 is a horizontal sectional view taken substantially along line 6-6of FIG. 3;

FIG. 7 is a vertical sectional view of a portion of the concrete footingfor a building and also showing in vertical section the upper portion ofthe pile cast there: in, together with the upper end anchorage means andtension-applying means for the post-tensionable reinforcement-sextending up through the pile;

FIG. 8 is a top plan view of such upper anchorage and post-tensioningmeans; and

FIG. 9 shows an alternative construction for the upper portion of thepile and with the reinforcement-anchoring and tension-applying andadjusting means located above the concrete footing and resting thereon.

Referring now to FIG. 1, a plurality of pile shells are indicated at 10.As shown, these comprise helically corrugated sectional step-taperedpile shells of a wellknown type, but it will be understood that pileshells or pipe of various other forms may be used. When necessary, andbefore the installation is completed, the earth is excavated, asindicated at 11, down to a point just below where the tops of the pilesare to be cut off or terminated, and to the full depth of the requiredfoundation footing, care being taken that the sides of the excavationare suitably supported or braced to protect the surrounding buildingfoundations or utilities from damage due to shifting of the soil.

The pile shells 10 may be installed at the desired locations by theprocedure of wet rotary pre-excavation, followed by the installation ofthe shells into the wet rotary pre-excavation holes, and then drivingthe shells to refusal through the clay or other soil indicated at 12,and into the hardpan below, as indicated at 13. In installing suchshells, methods may be followed like or similar to those disclosed inthe US. patent to Linton Hart, No. 2,663,152, granted December 22, 1953.As the next step, an inner sleeve as shown at 14 in FIG. 2, is installedin each pile shell 10, such sleeve being provided on its exterior withsuitable guide fins at various points, two of which are indicated at 15,to insure that it will remain approximately concentric with the shell10. The shells when driven are, in accord with usual practice, providedat their lower ends with suitable closure plates or socalled boots. Inthe particular form shown in FIG. 2 (although other forms may be used)the boots may comprise circular discs as at 16 secured in place as by aplow ring or the like 17, welded thereto and to the lower edge of thepile shell. When being installed, it will be understood that this bootplate has no central aperture, but acts to close off the end of theshell.

After installation of the inner sleeve 14, concrete as at 18 isintroduced into the shell around the outside of the sleeve 14 until thespace between the two is solidly filled, thus forming a solidly filledpile shell, except for the center core, through which subsequentope-rations hereinafter described are accomplished. Suitable drillingmeans is now introduced down into the sleeve 14 for drilling a centralaperture as at 19 through the boot plate 16. Then an addiitonal tube asat 20, which may be formed of telescoping sections, may be introducedand lowered or driven down through the hardpan or other soil andeventually lowered, if desired, for a short distance into the bore holeto be formed in the bedrock 21. The tube 20 acts as a connecting tubebetween the lower end of the pile per se and the bore hole which is tobe formed in the bedrock, but in some cases the character of the hardpanor soil may be such that the tube 20 may be dispensed with.

After the hole 19 has been drilled through the boot 16,. and the tube20, if used, has been lowered down through this hole, then by drillingor chopping, the bore hole is carried down through the hardpan or therefusal soil below the lower end of the pile shell, and thence, forexample by using a milling bit or other suitable bit, the hole isdrilled into the bedrock 21 for a suitable distance to provide foradequate engagement of the lower anchorage assembly (hereinafterdescribed) with the rock in the bore hole, and to assure that upliftingforces on the pile will be effectively resisted.

, The uplift pile assembly is now ready to receive the lower anchorageassembly, the details of one suitable example of which, among otherpossibilities, are shown in FIGS. 46 inclusive. Such assembly comprisesone or preferably a plurality of elements 23 in the form of steel rodsor preferably cables, as shown in the drawings, these elements beingsecurely attached at their lower ends in nose portions 24 by anysuitable known form of anchorage means or material, indicated at 25. Aplurality of wedge bars as at 26 respectively are slipped over eachcable or rod so that they will extend down at their lower ends intocontact with the nose portions, these wedge bars being formed with sidesurface portions as at 27 which will come into contact with each otheras shown in FIG. 5. A pipe or tremie 28 is now slid down centrallywithin the assembly to provide a withdrawable conduit for introducinggrout. Finally, in making up the anchorage assembly, gripper bars as at29 are placed in the spaces of sector-shaped cross-section between eachpair of the wedge bars 26. The assembly of parts may then be tiedtogether in any suitable manner as by surrounding same at various pointsby strands of soft iron wire or rope, or any other simple securingmeans, to retain the parts together until the assembly is lowered intoplace. The nose portions 24 if desired may be made in separablesections, one of which is indicated at 24a in FIG. 4a.

The anchorage assembly is now lowered into the pile through the innersleeve 14 (and through the connecting tube 20 if one is used) down intothe bore hole in the bedrock, preferably until the lower tip of the noseportions 24 engage the bottom of the bore hole. The cables or rods 23 attheir upper ends may then be cut off at proper length for attachment tothe upper anchorage assembly hereinafter described.

Such upper anchorage assembly, one typical and suitable form of whichamong other possibilities is shown in FIGS. 7 and 8, may now beinstalled. This assembly as shown comprises suitable screw anchor meansas indicated at 30, one being applied to the upper end of each of thecables or rods 23. Such screw anchors may be of a suitable known type,acting to secure the upper ends of the cables or rods 23 to screwelements as at 31. If desired, before the screw anchors 30 are put inplace, a supporting plate 32 may be slipped over the upper ends of thecables in position to rest upon surface 33 of the concrete within theupper end of the pile shell 10. Then, after the screw anchors aresecured in place on the cables, they may be surrounded by a casing 34,welded, if desired, at its lower edge to the supporitng plate 32 andhaving welded to the top thereof a cover-plate 35. Then lock washers 36are placed over the upwardly protruding threaded portions of the screwelements 31 and nuts 37 are screwed down in place thereon.

Each of the cables or rods 23 is then tensioned by screwing down thenuts 37. The cables or rods may be tensioned singly or in pairs, or allsimultaneously as preferred, and until they are subjected to a tensionat least substantially equal to the force of the required uplift whichthe pile is designed to resist. The tensioning of the rods or cables 23will cause the nose portions on the lower end of the lower anchorageassemblies to be pulled up against the lower ends of the wedge bars 26.As the wedge bars are forced upwardly, series of upwardly and inwardlyinclined surface areas thereon as indicated at 26' will engagerespectively corresponding downwardly and outwardly inclined surfaceareas 29' on the gripper bars 29,. thereby causing the latter to beforced outwardly and upwardly so that a series of external gripper teethas at 40 on the gripper bars 29 will engage the rock in the interior ofthe bore hole in the bedrock formation. Thus further upward movement ofthe wedge bars 26 and of the nose portions 24, as well as of the rods orcables 23, will be prevented and the latter will all become fixed andanchored at their lower ends and thus heavily post-tensioned by reasonof the fact that the upper ends thereof are secured under heavy tensionin the upper anchorage means above described.

At this stage, cement grout may be introduced down through the pipe 28-under pressure and by the use of suitable known grouting procedure, sothat as said pipe is raised, grout will penetrate and become set in thecavities between the various parts of the lower anchorage means forpermanently securing these parts against movement with respect to eachother and with respect to the bedrock. As the grouting proceedsupwardly, the cables will become surrounded and permanently protected bythe grout, which, if desired, may be extended up into the upperanchorage sleeve 34, although if this latter is not desired, theanchorage sleeve 34 may contain a concentric tube 43 for preventinggrout from surrounding the screw anchor means 30.

When the uplift piles have thus been post-tensioned to the requireddegree, and also preferably after the cables have been grouted in place,the ground and footing forms are then prepared for forming the finalconcrete foundation or footing as indicated at 41. Suitable reinforcingmeans may then be placed in such forms, including load-spreading means,if desired, of suitable known design to meet the requirements, whereuponthe concrete for the footing may be poured to surround the upperanchorage assemblies. As indicated in FIG. 7, the upper anchorageassemblies will then serve to anchor the upper end portions in the pilestructures to the footing by reason of being encased in the concrete ofthe footing.

In some cases, it may be preferable to pour the concrete footing asshown at 50 in FIG. 9 before the posttensioning of the piles is carriedout. In this case, the

pile shell as at may extend up to the level of the top surface of thefooting and with a top anchorage assembly as indicated at 51 positionedto rest upon the top surface of the concrete in the pile shell, and alsoon the surrounding top surface of the footing, if desired. The assembly51 may be otherwise similar to that shown in FIG. 7. With thisarrangement it will be possible to adjust and readjust the degree ofpost-tensioning as may he required from time to time as conditionschange durmg the construction work and as the construction of thebuilding on the footing proceeds.

Although certain particular embodiments of the invention are hereindisclosed for purposes of explanation, further modifications thereof,after study of this specification, Will be apparent to those skilled inthe art to which the invention pertains. Reference should accordingly behad to the appended claims in determining the scope of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. Method of installing a pile construction adapted to support astructure and also to resist upheaval of the soil surrounding the pile,which method comprises: introducing a pile shell down to a firm bearingin the earth; introducing a filling of concrete in said shell, butleaving a hole extending down therethrough; introducing drilling meansthrough said hole and boring therewith a hole down for a substantialdistance into bedrock as well as through any earth intervening betweenthe lower end of the pile and such bedrock; withdrawing the drillingmeans; introducing an assembly including anchorage means for engagingthe bedrock in the hole bored therein and for resisting upwarddisplacement of said assembly, said assembly including a posttensionable element or elements extending from such anchorage means upto the top of the pile shell; providing anchoring means at the upper endof said element or elements and applying and maintaining tension in saidelement or elements at least substantially equal to the upheaval forceswhich the pile construction is to resist, such tension being maintainedbetween said lower anchorage means and the upper portion of the pilewhich becomes post-stressed thereby under compression.

2. Method of installing a pile construction adapted to support astructure and also to resist adjacent soil upheaval, which methodcomprises: driving a booted pile shell to a firm bearing in the earth;introducing a pipe into said shell and extending down to the boottherein; introducing a filling of concrete into the space between saidpipe and shell; using boring means extending down through said pipe forboring therewith a hole through the boot and down for a substantialdistance into bedrock as well as through earth intervening between theboot and such bedrock, a connecting tube being introduced effectively toconnect said pipe with the hole bored in the bedrock; introducingthrough said pipe, tube and hole an assembly including anchorage meansfor engaging the bedrock in the hole bored therein and for resistingupward displacement of said assembly, said assembly including apost-tensionable element or elements extending from such anchorage meansup to the top of the pile shell; providing anchoring means at the upperend of said element or elements and applying and maintaining heavytension in said element or elements between said lower anchorage meansand the upper portion of the pile which becomes thereby post-stressedunder compression.

3. Method of installing a pile and concrete footing construction adaptedto support a structure and also to resist upheaval of the soilsurrounding the pile, which method comprises; driving a pile shell intothe earth; and introducing a filling of concrete in said shell, leavinga hole therethrough, such concrete being allowed to set in the shell toprovide a rigid pile; using drilling means extending down through saidshell and boring therewith a hole down for a substantial distance intobedrock as well as through any earth intervening between the lower endof the pile and such bedrock; casting in engagement with the upper endof the shell and the filling of concrete, a concrete footing forsupporting said structure and hearing against a substantial area of thesurrounding soil, such footing and filling being affixed to one another;introducing an assembly including anchorage means for engaging thebedrock in the hole bored therein, said assembly including apost-tensionable element or elements extending from such anchorage meansup to the top of the pile shell; applying anchoring means to the upperend of said element or elements and applying and maintaining a heavytension in said element or elements between said lower anchorage meansand the upper portion of the pile, the upper end of the anchoring meansbeing exposed to permit adjustment of said forces; and the pile becomingpoststressed under compression upon tensioning said element or elements.

References Cited in the file of this patent UNITED STATES PATENTS1,164,085 Golds borough Dec. 14, 1915 1,558,127 Upson Oct. 20, 19252,428,070 Frenkil Sept. 30, 1947 2,435,345 Freyssinet Feb. 3, 19482,570,003 Palmer Oct. 2, 1951 2,589,484 Ecuer Mar. 18, 1952 2,706,498Upson Apr. '19, 1955 2,741,910 Thornley Apr. 17, 1956 2,863,292 Coyne etal. Dec. 9, 1958 2,917,901 Lackner Dec. 22, 1959 FOREIGN PATENTS 699,615Great Britain Nov. 11, 1953 763,899 Great Britain Dec. 19, 1956

1. METHOD OF INSTALLING A PILE CONSTRUCTION ADAPTED TO SUPPORT ASTRUCTURE AND ALSO TO RESIST UPHEAVAL OF THE SOIL SURROUNDING THE PILE,WHICH METHOD COMPRISES: INTRODUCING A PILE SHELL DOWN TO A FIRM BEARINGIN THE EARTH; INTRODUCING A FILLING OF CONCRETE IN SAID SHELL, BUTLEAVING A HOLE EXTENDING DOWN THERETHROUGH; INTRODUCING DRILLING MEANSTHROUGH SAID HOLE AND BORING THEREWITH A HOLE DOWN FOR A SUBSTANTIALDISTANCE INTO BEDROCK AS WELL AS THROUGH ANY EARTH INTERVENING BETWEENTHE LOWER END OF THE PILE AND SUCH BEDROCK; WITHDRAWING THE DRILLINGMEANS; INTRODUCING AN ASSEMBLY INCLUDING ANCHORAGE MEANS FOR ENGAGINGTHE BEDROCK IN THE HOLE BORED THEREIN AND FOR